Caring for dogs
Take care of your dogs with food, and use toys to play with them. Play with the dogs are a good way to bond with them. You can let them out into the backyard, and if there is more than one dog there they will play with each other.
Coins
Complete missions to earn coins. To start missions, go the lobby then tap the area in front of the computer to view the current dog cards. Dog cards will show you what type of care each specific dog requires for that day. After you have completed caring for all of the dogs, use the button with the moon and the stars to end the day and collect your rewards. If that button is tapped before your complete your mission, it will only advance to the next day.
Upgrades
Most upgrades are just cosmetic. You can start upgrading after reaching level 5. However, you will first need to upgrade your lobby before other upgrades can be accessed. The best upgrade is the enclosure, allowing you to cater your services for more dogs at once.